1. Field of the Invention
This invention relates to an anti-suntan cosmetic composition and, more particulary, to an anti-suntan cosmetic composition comprising a specific zinc oxide which scatters or absorbs ultraviolet rays, especially those in UV-A region, harmful to the skin. The skin can be protected from suntan by the anti-suntan cosmetic composition, so that the skin would not be blotched or freckled and also be prevented from aging.
2. Description of the Prior Art
As an anti-suntan cosmetic composition, ultraviolet absorbers or titanium oxide having specific particle size have been conventionally used. Such anti-suntan cosmetic compositions absorb or scatter ultraviolet rays of wavelength in a high energy region near 250-350 nm, by which the skin would be inflammed.
As a result of the recent progress for the study on harmfulness of ultra-violet rays, it has been found that ultraviolet rays in the UV-A region of from 320 to 400 nm, by which the skin is sun-tanned, cause blotches and freckles and promote the skin aging. Therefore, ultraviolet rays in the UV-A region, as well as ultraviolet rays in the UV-B region of from 250 to 320 nm, by which the skin is sun-burned, are considered to be harmful to the skin. In view of the above, absorbers for UV-A region ultraviolet rays was developed recently (refer to Japanese Patent Application Laid-Open No. 62517/1984).
However, these ultraviolet ray (UV-A) absorbers are organic compounds and yet involve various problems in the safety and the lasting effect thereof.
On the other hand, there have been made various studies on absorption and scattering of UV-ray and it has been known that a certain kind of inorganic powder has a great effect particularly for interrupting ultraviolet rays.
It has generally be known that powder having a higher reflective index has greater hiding power and has greater UV-ray interrupting effect. Upon measuring the optical transmittance of various metal oxides (those conventionally used for cosmetics having particle size of 0.5 m.mu.) having a high reflective index, it was confirmed that the optical transmittance at the wavelength region from 250 to 700 nm was substantially constant (FIG. 1).
The metal oxides having an adequate UV prevention effect, thus, involve an excessive hiding power which gives unacceptable feeling to the users, so that they are not suitable as an ingredient of anti-suntan cosmetic compositions, although they are easily available.
As described above, there have not yet been provided those absorbers for ultraviolet rays in the UV-A region, which are harmless, useful, and easily and inexpensively available.